How to prove cause leads to effect

摘要

IT'S one of the fundamental problems in science: when two events take place, can we tell whether one directly caused the other, or if the two follow a similar pattern for a different reason?Separating correlation and causation is notoriously difficult. People might become more tanned when they eat more ice cream, but that doesn't mean ice cream gives you a tan; it probably just means it's summer.In many cases the link between two variables seems more likely to be causal - for instance, smoking and lung cancer, or atmospheric carbon dioxide levels and climate change.